Is there a relationship between back squat depth, ankle flexibility, and Achilles tendon stiffness?

Area of Science:

• Biomechanics
• Sports Science
• Musculoskeletal Research

Background:

• Achieving optimal back squat depth is crucial for training effectiveness and injury prevention.
• Factors influencing squat depth, such as ankle mobility and tendon properties, require further investigation.

Purpose of the Study:

• To examine the relationship between back squat depth capacity and ankle dorsiflexion range of motion (ROM), resistance to stretch, and Achilles tendon stiffness.
• To identify key biomechanical factors limiting squat depth in healthy individuals.

Main Methods:

• 2D kinematic analysis was used to assess back squat depth capacity.
• Ankle dorsiflexion maximal ROM was measured using smartphone goniometry (lunge test) and isokinetic dynamometry (prone test).
• Achilles tendon stiffness was evaluated using shear wave elastography (SWE) at rest and during isometric contraction via B-mode sonography.

Main Results:

• Back squat depth was significantly associated only with ankle dorsiflexion ROM during the lunge test (r=0.69, p=0.001).
• Ankle dorsiflexion ROM in the lunge test correlated with ankle resistance to stretch (r=0.46, p=0.050) and Achilles tendon stiffness-SWE (r=0.62, p=0.005).
• Ankle dorsiflexion ROM in the lunge test was the sole significant differentiator between individuals with low and high squat depth capacity (p=0.014).

Conclusions:

• Back squat depth is predominantly influenced by ankle dorsiflexion range of motion when the knee is flexed.
• Global joint and Achilles tendon mechanical properties did not show a significant influence on squat depth capacity in this cohort.
• Improving ankle dorsiflexion ROM may be key for enhancing back squat depth.